Free PINS on the Cyclone iv in OSSC V1.5?

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  • #19615
    renegadeandy
    Participant

    Hi all,

    I am looking for some gpio pins which are not used by the v1.5 ossc as per:

    https://www.niksula.hut.fi/~mhiienka/ossc/diy-v1.5/ossc_v1.5-diy_schematic.pdf

    Using the Quartus Prime software, specifically the Pin Planner I created a pin finder for 3.3v Assignment == Unassigned, which to me is exactly what I am looking for. It suggests the following pins but the schematic pdf above makes me think they are being used? Am I reading the schematic wrong?

    Schematic

    The schematic has labels next to the red arrows and then inside the chip blue pin writing….not sure if the significance of the labels:

    6 – ASDO DATA1
    8 – nCSO FLASH_nCE
    12 – DCLK DCLK
    13 – DATA0 DATA0
    24 – CLK2
    126 – CLK8

    Am I free to use any of those pins above?

    #19856
    renegadeandy
    Participant

    Any thoughts on this? Does it look right?

    #19861
    marqs
    Participant

    You should not use any pins connected to the flash chip. Unused CLK* pins (normally wired to gnd) are free but they can be only used as inputs. Note that SD card DAT1 and DAT2 pins are not used in SPI mode and are already wired to the socket, so those would be the easiest to take advantage of.

    #19864
    renegadeandy
    Participant

    Am i right in saying marqs:

    6 – input/output
    12 – input
    13 – input/output
    24 – input
    126 – input

    Are those pins OK? Any others?

    #19925
    marqs
    Participant

    Pins 6, 12 and 13 are also connected to flash. You should only use 24,126 (input only) and 28,39 (I/O with 10k pullup).

    #19935
    renegadeandy
    Participant

    marqs,

    How should I know that I could use those pins, given the schema in my first post and the pin planner in the ossc project, I find it very hard to determine that those pins are indeed free. Pin 28 for example says SD_DAT2 — What does this mean? Why is it there? Should I just ignore that? How am I supposed to know what is what?

    #19958
    marqs
    Participant

    My earlier post above explains why SD_DAT1 and SD_DAT2 may be used even though they are connected by default.

    #19962
    renegadeandy
    Participant

    Can you answer the specific questions ?

    Q1/How should I know that I could use those pins, given the schema in my first post and the pin planner in the ossc project. I find it very hard to determine that those pins are indeed free.

    Pin 28 for example says SD_DAT2 — What does this mean? Why is it there? If they are not used in SPI mode, then why are they labelled as in use on the schema? Are you now saying Should I just ignore that? How am I supposed to know what is what?

    #20018
    marqs
    Participant

    If you look into RTL (ossc.v) or Quartus compilation log, you’ll notice that SD_DAT[1] and SD_DAT[2] have no drivers in current implementation. Those pins originally were wired to microSD socket so that 4-pin SD mode could possibly be supported in future, but currently SPI mode is good enough for the purpose and there’s no plans to implement SD mode anytime soon.

    #26115
    renegadeandy
    Participant

    Hi again

    So the SD card functionality uses SPI — which uses 4 signals:

    SCLK
    MOSI
    MISO
    SS

    Is that correct? Can you help me locate those pin numbers?

    I see in the Pin editor:

    SD_CLK
    SD_CMD
    SD_DAT[3]
    SD_DAT[2]
    SD_DAT[1]
    SD_DAT[0]

    — how do those tie up the SPI spec?

    #26133
    marqs
    Participant

    SD card pinout. SD_DAT[2] are SD_DAT[1] are unused in SPI mode.

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